1. Field of the Invention
The present invention relates to a method of manufacturing an array of vertical nanochannels and a method of manufacturing a nanodot using the array, and more particularly, to a method of forming a self-ordered nanochannel-array by two-step anodizing and a method of fabricating a nanodot using the nanochannel-array.
2. Description of the Related Art
Recently, researches have been actively conducted to form nano-scale patterns or structures in memories, laser diodes (LDs), photo diodes (PDs), transistors, far-infrared detectors, solar cells, optical modulators, and the likes. For example, a nanodot associated with an electronic control changes the n umber of bound electrons in correspondence to its size. Since electronic devices using nanodots can be actuated with a smaller number of electrons compared to conventional electronic devices, a threshold current level is lowered to enable low voltage actuation. The devices using nanodots also have the advantage of offering a high throughput with low voltage.
A conventional nanodot fabrication method utilizes a traditional deposition process including low pressure chemical vapor deposition (LPCVD) to form Si/Si3N4 nuclei or sprays nanoparticles onto a substrate. However, the conventional approach makes it difficult to control the sizes of nanoparticles. Furthermore, spraying nanoparticles of an equal size cannot guarantee uniform nanodot distribution.
Another conventional method is to use electron beam lithography or laser beam lithography. This approach not only makes it difficult to obtain a nanodot of the desired size due to process limitation but also suffers from restriction in reducing its size. Furthermore, it is well known that lithography is a complicated and expensive process.
Meanwhile, Stephen Y. Chou et al. have proposed a method of forming a metal nanodot on a silicon substrate. This method involves imprinting a PMMA layer formed on a silicon substrate with a mold, forming a channel array to a predetermined depth, removing the residual PMMA from the bottom of a channel and forming a metal layer on the resulting structure, and soaking the substrate in an etching solution and lifting off the PMMA layer and residual metal thereon (Appl. Phys. Lett., Vol. 67. No. 21. 20 Nov. 1995). According to this technique, the size or spacing of a nanodot is determined by the mold. That is, the nanodot size is limited by a microscale patterning of the mold such as photolithography. Thus, its size cannot be reduced to less than the limit allowed in a photolithography process.
Hideki Masuda et al. have proposed a method of manufacturing a nanochannel-array that can be usefully used for developing various nanoscale devices (Appl. Phys. Lett. 71(19), 10 Nov. 1997). This method involves performing compression molding on a shallow concavity, carrying out an anodizing process, and forming a self-ordered channel-array. However, this method has a problem in that the size of each channel or array is limited by the mold.